Methods for preserving state across a failure and devices thereof

ABSTRACT

A method, non-transitory computer readable medium, and host device that receives one or more transactions. A state is stored in a transaction log in a volatile memory wherein the state includes information associated with the one or more transactions. The transaction log is stored in a stable storage device when a failure is determined to a have occurred. The transaction log can then be retrieved and replayed subsequent to a reboot. Thereby, state can be preserved and transactions pending, but not yet committed to storage server devices, can be replayed and proceed with minimal or no impact on the client devices originating the write transactions.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 14/088,134, filed Nov. 22, 2013, which is hereby incorporated by reference in its entirety.

FIELD

This technology generally relates to storage systems and, more particularly, to methods and devices for preserving state stored by a virtual storage controller across a failure.

BACKGROUND

A storage fabric may include multiple storage controllers to store and manage data on behalf of client devices. A storage controller may be a physical device or virtual appliance (also referred to herein as a virtual storage controller), each with their own instance of an operating system. The operating system may operate independently as a single node, or coordinate a cluster of nodes as a single system.

A physical storage controller in a storage fabric can utilize non-volatile memory to store critical state (e.g., a transaction log for write transactions which are staged prior to being committed to disk) in the physical storage controller device. Since the memory is non-volatile, the stored information will persist should there be a failure in order to allow the critical state, including any pending write transactions at the time of the failure for example, to be maintained.

However a virtual storage controller in the storage fabric may not have access to suitable non-volatile memory of a host device on which the virtual storage controller is executing. Alternatively, access to suitable non-volatile memory may be complex and/or difficult to obtain and/or manage and may be different for various providers of host devices.

Accordingly, critical state, such as a transaction log in one example, is maintained by each of the virtual storage controllers in a volatile memory and is synchronously flushed to a persistent or non-volatile data storage device, such as a disk on one of the storage server devices in the storage fabric, in order to allow the virtual storage controllers to maintain the critical state. However, the synchronous flushing of transaction log information is expensive and limits the speed with which the virtual storage controllers can perform write operations, which is undesirable.

SUMMARY

A method for preserving state across a failure includes receiving with a virtual storage controller executed by a host device one or more transactions. A state is stored with the virtual storage controller in a transaction log in a volatile memory wherein the state includes information associated with the one or more transactions. The transaction log is stored with the virtual storage controller in a stable storage device when a failure is determined to a have occurred.

A non-transitory computer readable medium having stored thereon instructions for preserving state across a failure comprising machine executable code which when executed by a processor, causes the processor to perform steps including receiving one or more transactions. A state is stored in a transaction log in a volatile memory wherein the state includes information associated with the one or more transactions. The transaction log is stored in a stable storage device when a failure is determined to a have occurred.

A host device includes a processor coupled to a memory and configured to execute programmed instructions stored in the memory to generate a virtual storage controller configured to perform steps including receiving one or more transactions. A state is stored in a transaction log in a volatile memory wherein the state includes information associated with the one or more transactions. The transaction log is stored in a stable storage device when a failure is determined to a have occurred.

With this technology, critical state can be preserved across a failure for a virtual storage controller operating in a storage fabric. With respect to software failures requiring a reboot, this technology allows a transaction log to be stored from a volatile memory to a stable storage device upon the failure being detected and later retrieved and replayed subsequent to the reboot. Thereby, state can be preserved and transactions, including write transactions pending, but not committed to storage server devices at the time of the failure, can be replayed and proceed with minimal or no impact on the client devices originating the write transactions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a network environment with a storage fabric which incorporates an exemplary host device;

FIG. 2 a block diagram of the exemplary host device; and

FIG. 3 is a flowchart of an exemplary method for preserving state across a failure.

DETAILED DESCRIPTION

A network environment 10 illustrating a storage fabric with an exemplary host device 12 is illustrated in FIG. 1. The environment 10 further includes client devices 14(1)-14(n), and storage server devices 16(1)-16(n), although this environment 10 can include other numbers and types of systems, devices, components, and/or elements in other configurations, such as multiple numbers of each of these apparatuses and devices. The client computing devices 14(1)-14(n) are in communication with the host device 12 through communication network 18(1) and the host device 12 is in communication with the storage server devices 16(1)-16(n) through communication network 18(2). The communication networks 18(1) and 18(2) can be local area networks (LANs), wide area networks (WANs), or combination thereof, for example. This technology provides a number of advantages including methods, non-transitory computer readable medium, and devices that facilitate the preservation of critical state across a software failure allowing transactions to be replayed.

Each of the client devices 14(1)-14(n) in this example can include a processor, a memory, a communication interface, an input device, and a display device, which are coupled together by a bus or other link, although each of the client devices can have other types and numbers of components or other elements and other numbers and types of network devices could be used. The client devices 14(1)-14(n) may run interface applications that provide an interface to make requests for and send content and/or data to the host device 12 via the communication network 18(1), for example. Each of the client devices 14(1)-14(n) may be, for example, a conventional personal computer (PC), a workstation, a smart phone, a virtual machine, or other processing and/or computing device.

Each of the storage server devices 16(1)-16(n) in this example include, a stable storage device 32(1)-32(n), a processor, and a network interface coupled together by a bus or other link. The stable storage device 32(1)-32(n) in this example can include conventional magnetic disks or any other type of storage device suitable for storing large quantities of data. The storage server devices 16(1)-16(n) may be organized into one or more volumes of Redundant Array of Inexpensive Disks (RAID), although other types and numbers of storage server devices in other arrangements can be used.

The host device 12 in this example operates on behalf of the client devices 14(1)-14(n) to store and manage shared files or other units of data in the storage server devices 16(1)-16(n). Accordingly, the host device 12 also manages the storage server devices 16(1)-16(n) in this example and receives and responds to various read and write requests from the client devices 14(1)-14(n), directed to data stored in, or to be stored in, one or more of the storage server devices 16(1)-16(n).

Referring more specifically to FIG. 2, a block diagram of the exemplary host device 12 is illustrated. In this example, the host device 12 includes a processor 20, a volatile memory 22, a network interface 24, and a virtual storage controller 26, coupled together by a bus 28 or other communication link. In this example, the bus 26 is a Peripheral Component Interface (PCI), although other bus types and links may be used.

The processor 20 of the host device 12 may execute one or more programmed instructions stored in a memory of the host device 12 for the functions and/or other operations illustrated and described herein. For example, the memory can store instructions comprising a system operating system that when executed by the processor 20 generates a hypervisor that interfaces hardware of the host device 12 with the virtual storage controller 26, such as through a virtual machine, for example, although the virtual storage controller 26 can be executed and implemented in other manners. The processor 20 of the host device 12 may include one or more central processing units and/or general purpose processors with one or more processing cores, for example.

The volatile memory 22 of the host device 12 may include any of various forms of random access memory (RAM), for example. In this example, the virtual storage controller 26 does not have access, or an interface, to a non-volatile memory or other stable storage device that may be present on the host device 12. In some examples, the virtual storage controller 26 is provided by a different vendor than that of the host device 12 and specific aspects of the integration may not be available in order to provide a suitable interface to a stable storage device.

Accordingly, the volatile memory 22 in this example stores a transaction log 30, as described and illustrated in more detail later, although the memory can store other types and amounts of other data, including other critical state information. The transaction log 30 in this example is used by the virtual storage controller 26 to stage write transactions received from the client devices 14(1)-14(n) prior to committing the write transactions to the storage server devices 16(1)-16(n), as described and illustrated in more detail later. In other examples, the transaction log 30 can be used by the operating system 28 to store a support log and, in yet other examples, the transaction log is used to store other natively-generated transactions. The transaction log 30 can also be used to store other types and numbers of transactions and other critical state information.

The network interface 24 of the host device 12 in this example can be an Ethernet adapter, for example, operatively coupling and communicating between the host device 12 and the client devices 14(1)-14(n), which are coupled together by the communication network 18(1), although other types and numbers of communication networks or systems with other types and numbers of connections and configurations to other devices and elements also can be used.

By way of example only, the communication networks 18(1) and 18(2) can use TCP/IP over Ethernet and industry-standard protocols, including NFS, CIFS, SOAP, XML, LDAP, and SNMP, although other types and numbers of communication networks, can be used. The communication networks 18(1) and 18(2) in this example may employ any suitable interface mechanisms and network communication technologies including, for example, teletraffic in any suitable form (e.g., voice, modem, and the like), Public Switched Telephone Network (PSTNs), Ethernet-based Packet Data Networks (PDNs), combinations thereof, and the like. The communication networks 18(1) and 18(2) may also comprise any wide area network (e.g., Internet), although any other type of traffic network topology may be used.

Although examples of the host device 12, client devices 14(1)-14(n), and storage server devices 16(1)-16(n) are described herein, it is to be understood that the devices and systems of the examples described herein are for exemplary purposes, as many variations of the specific hardware and software used to implement the examples are possible, as will be appreciated by those skilled in the relevant art(s). In addition, two or more computing systems or devices can be substituted for any one of the systems in any embodiment of the examples.

The examples also may be embodied as a non-transitory computer readable medium having instructions stored thereon for one or more aspects of the present technology as described and illustrated by way of the examples herein, as described herein, which when executed by the processor, cause the processor to carry out the steps necessary to implement the methods of this technology as described and illustrated with the examples herein.

An exemplary method for preserving state across a failure will now be described with reference to FIGS. 1-3. Referring more specifically to FIG. 3, in step 300 in this example, the virtual storage controller 26 executing on the host device 12 receives transactions, such as natively-generated transaction(s) from the operating system 28 and/or write transaction(s) from one or more of the client devices 14(1)-14(n), for example. In one example, the transactions can include requests from the operating system 28 to store support information on one or more of the storage server devices 16(1)-16(n). In another example, the transactions received from the client devices 14(1)-14(n) can be requests from the client devices 14(1)-14(n) to store information on one or more of the storage server devices 16(1)-16(n). Other types and/or numbers of transactions may be received in step 300.

In step 302 in this example, the virtual storage controller 26 executing on the host device 12 stages the received transactions and stores information associated with the transactions in the transaction log 30. As described and illustrated earlier, the transaction log 30 can be stored in the volatile memory 22 of the host device 12. Accordingly, the state of the virtual storage controller 26 is stored in the transaction log 30. In this example, the state includes the transactions and other contextual information and/or metadata, if any, useful for subsequent processing of the transactions, although other types and/or amounts of information may be included in the state of the virtual storage controller 26. In this example, the transactions are staged because they may be received more quickly than they can be processed by the virtual storage controller 26. Generally, processing and committing the transactions to the storage server devices 16(1)-16(n) requires a relatively long period of time considering the mechanical nature of the operation of storing data on disks of the storage server devices 16(1)-16(n). Following the staging of transactions in the transaction log 30, the virtual storage controller 26 continued receiving transactions in step 300, as described and illustrated earlier.

Additionally, in parallel and asynchronously, the virtual storage controller 26 executing on the host device 12 in this example determines a system failure has occurred in step 304. By way of example only, the operating system associated with the virtual storage controller 26 can determine a software failure has occurred when the system enters a panic state, although other types and/or numbers of situations could occur that also result in determining a failure has occurred.

Following a determination by the virtual storage controller 26 executing on the host device 12 that there has been a failure, in step 306 in this example, the virtual storage controller 26 executing on the host device 12 stores the state including at least a portion of the associated transaction log 30 in a stable storage device, such as one or more of the stable storage devices 32(1)-32(n) of one or more of the storage server devices 16(1)-16(n). While the virtual storage controller 26 may not have access to other non-volatile memory that may be present on the host device 12, it does have access to a stable storage device 32(1)-32(n) of each of the storage server devices 16(1)-16(n) with which it communicates to process transactions. However, in other examples, other locations for preserving the transaction log 30 can also be used including a local storage drive attached to the host device 12 or an off-box transaction log database service, for example.

Accordingly, the virtual storage controller 26, or more specifically the operating system 28, can be configured to automatically store at least a portion of the current contents of the associated transaction log 30 in a default or preselected stable storage device 32(1)-32(n) of one or more of the storage server devices 16(1)-16(n) upon detecting entry into a software failure. By flushing the transaction log 30 upon detecting entry into a software failure into a stable storage device 32(1)-32(n) of one or more of the storage server devices 16(1)-16(n), the virtual storage controller 26 can preserve its state and, in particular, information associated with transaction(s) currently pending at the time of the failure.

In step 308, the virtual storage controller 26 executing on the host device 12 determines whether the associated operating system 28 has successfully rebooted, although other approaches for identifying a successful reboot may be used. If the virtual storage controller 26 determines that it has not successfully rebooted, then the No branch is taken back to step 312 and the virtual storage controller 26 effectively waits for the operating system 28 to reboot successfully. If the virtual storage controller 26 determines that it has successfully rebooted, then the Yes branch is taken to step 314

In step 310, the virtual storage controller 26 executing on the host device 12 retrieves the associated transaction log 30 from the stable storage device 32(1)-32(n) of the one or more of the storage server devices 16(1)-16(n) at which the information was stored in step 310. Accordingly, the virtual storage controller 26 can be configured to automatically retrieve the state information, including previously stored information associated with pending transactions from the retrieved transaction log 30, upon successfully rebooting subsequent to a failure.

In this example, the volatile memory 22 that stores the associated transaction log 30 will have been erased during the rebooting of the virtual storage controller 26. However, the information associated with the pending transaction(s) in the transaction log 30 was stored, in step 310 in this example, in a stable storage device 32(1)-32(n) of the one or more of the storage server devices 16(1)-16(n). As the stable storage device 32(1)-32(n) of the one or more of the storage server devices 16(1)-16(n) will not be erased as a result of the reboot, the state of the virtual storage controller 26 can thereby be preserved.

Accordingly, in step 312 in this example, the virtual storage controller 26 executing on the host device 12 replays the transaction(s) in the transaction log 30 proximate to the time of the failure, as retrieved in step 314. By replaying the transactions, data sent by one or more of the client devices 14(1)-14(n) to the virtual storage controller 26 can be committed to one or more of the storage server devices 16(1)-16(n) with reduced or no impact on the client devices 14(1)-14(n) as a result of the failure of the one of the virtual storage controllers 34(1)-34(n). Additionally, other transactions, including transactions natively generated by the operating system 28, can also advantageously be replayed in step 316.

With this technology, a virtual storage controller that does not have suitable access to non-volatile memory of a host device can flush pending transaction(s) upon failure to a stable storage device. Accordingly, upon rebooting and erasing a transaction log, information associated with the transactions can be retrieved from the stable storage device and advantageously replayed thereby preserving the state of the virtual storage controller across a failure. By preserving the state across a failure, the experience of client devices, for example, originating transactions is advantageously improved as the transactions pending upon the failure of the virtual storage controller are able to be committed to stable storage device(s) rather than dropped resulting in an error message and/or data loss. Additionally, performance is improved with this technology as a result of the asynchronous preservation of transactions. Since transactions are preserved asynchronously and upon failure, the expense of writing each individual transaction to stable storage upon processing the transaction is not incurred and transactions can therefore be processed relatively quickly.

Having thus described the basic concept of the invention, it will be rather apparent to those skilled in the art that the foregoing detailed disclosure is intended to be presented by way of example only, and is not limiting. Various alterations, improvements, and modifications will occur and are intended to those skilled in the art, though not expressly stated herein. These alterations, improvements, and modifications are intended to be suggested hereby, and are within the spirit and scope of the invention. Additionally, the recited order of processing elements or sequences, or the use of numbers, letters, or other designations therefore, is not intended to limit the claimed processes to any order except as may be specified in the claims. Accordingly, the invention is limited only by the following claims and equivalents thereto. 

What is claimed is:
 1. A method for preserving state across a failure, the method comprising: receiving, with a virtual storage controller executed by a host device, one or more transactions; storing, with the virtual storage controller, a state in a transaction log in a volatile memory, the state comprising information associated with the one or more transactions; determining, with the virtual storage controller, when a failure has occurred; and storing, with the virtual storage controller, the transaction log in a stable storage device when the failure is determined to a have occurred.
 2. The method of claim 1 wherein the host device includes the volatile memory and the storing further comprises storing the transaction log in the volatile memory of the host device.
 3. The method of claim 1 further comprising retrieving, with the virtual storage controller, the transaction log from the stable storage device subsequent to detecting a successful reboot.
 4. The method of claim 3 further comprising replaying, with the storage controller device, one or more write transactions of the one or more transactions included in the retrieved transaction log.
 5. The method of claim 1 wherein the failure is a software failure associated with an operating system of the virtual storage controller.
 6. A non-transitory computer readable medium having stored thereon instructions for preserving state across a failure comprising machine executable code which when executed by a processor, causes the processor to perform steps comprising: receiving one or more transactions; storing a state in a transaction log in a volatile memory, the state comprising information associated with the one or more transactions; determining when a failure has occurred; and storing the transaction log in a stable storage device when the failure is determined to a have occurred.
 7. The medium of claim 6 wherein a host device includes the volatile memory and the storing further comprises storing the transaction log in the volatile memory of the host device.
 8. The medium of claim 6 wherein the machine executable code when executed by the processor further causes the processor to perform steps further comprising retrieving the transaction log from the stable storage device subsequent to detecting a successful reboot.
 9. The medium of claim 8 wherein the machine executable code when executed by the processor further causes the processor to perform steps further comprising replaying one or more write transactions of the one or more transactions included in the retrieved transaction log.
 10. The medium of claim 6 wherein the failure is a software failure associated with an operating system of a virtual storage controller.
 11. The medium of claim 6 wherein the plurality of transactions are received at a virtual storage controller executed by a host device and the storing the state, determining, and storing the transaction log in a non-volatile memory steps are performed by the virtual storage controller.
 12. A host device, comprising: a processor coupled to a memory and configured to execute programmed instructions stored in the memory to generate a virtual storage controller configured to perform steps comprising: receiving one or more transactions; storing a state in a transaction log in a volatile memory, the state comprising information associated with the one or more transactions; determining when a failure has occurred; and storing the transaction log in a stable storage device when the failure is determined to a have occurred.
 13. The device of claim 12 wherein the memory is the volatile memory and the storing further comprises storing the transaction log in the volatile memory of the host device.
 14. The device of claim 12 wherein the virtual storage controller is further configured to perform steps further comprising retrieving the transaction log from the stable storage device subsequent to detecting a successful reboot.
 15. The device of claim 14 wherein the virtual storage controller is further configured to perform steps further comprising replaying one or more write transactions of the one or more transactions included in the retrieved transaction log.
 16. The device of claim 12 wherein the virtual storage controller is further configured to perform steps further comprising removing one or more entries of the transaction log as one or more write transactions associated with the one or more entries are committed. 